The present invention relates to packaging for integrated circuits and, more particularly, to integrated circuit packages suitable for operation at microwave compatible frequencies.
A major objective of the present invention is to provide circuit packaging including a large number, e.g., more than eight, of high quality power lines and signal lines to a digital-to-analog converter integrated circuit used at data rates on the order of one gigahertz (GHz). Conventional packages for high data rate integrated circuits use a sapphire substrate to carry both signal lines and power sources. For example, 50-ohm signal lines can be made with 10-mil wide gold traces deposited on the sapphire. Power is routed from the edge of the sapphire to the integrated circuit along dedicated lines. As close to the integrated circuit as possible, monoblock capacitors bypass these power lines to ground. The ground connections can be made using plated-through vias to a ground plane on the back of the sapphire.
Individual monoblock capacitors consume considerable area on the scale of the sapphire packaging. Where many such capacitors are required, they must be placed several millimeters from the integrated circuit chip. The monoblock capacitors are then connected by transmission lines to the chip. These transmission lines typically have impedances greater than 20 ohms, which can impede voltage stabilization after switching. Delays in voltage stabilization appear as noise at the device output and limit the ultimate speed of the integrated circuit. In addition, the high impedance transmission lines can introduce noise and cause cross-talk.
What is needed is a package for high speed integrated circuits which provides for large numbers of transmission and power lines. The power lines should permit rapid and relatively noise-free current switching.